Last



y 14, 1963 KAMBORlAN 3,089,166

LAST

Filed Dec. 1, 1961 a: Y H I INVENTOR.

uZ/JZIZ lawziarza' 2 LAST Albert Karnborian, Newton Center, Mass, assignor to International Shoe Machine Corporation, Boston, Mass, a corporation of Massachusetts Filed Dec. 1, 1961, Ser. No. 156,245 8 Claims. (Cl. 12-141) This invention relates to apparatus for manufacturing shoes and, in particular, to lasts for receiving an upper assembly preparatory to lasting.

Conventionally, in the manufacture of shoes, the insole is temporarily attached to the bottom of the last by means of fasteners, such as tacks, to hold it in place during lasting of the upper thereto. Constant use of the tacks for successive shoe making operation eventually destroys the bottom of the last and for this reason it is customary to place removable inserts in the bottom of the last, for receiving the tacks, which may be removed when worn out and replaced. While this lengthens the life of the last considerably, driving the tacks and then removing them involves additional operations which take time and the hazard of a tack or tacks being inadvertently left in the shoe.

It is the object of this invention temporarily to attach the insole to the last with a material which will not leave a residue on the insole and can be used over-and-over again without loss of its adhesive characteristics, thereby eliminating the use of fastening elements which must be applied and removed prior to and after each lasting operation.

This is effected herein by attaching a material to the bottom of the last which is characterized in that it is activatable for a predetermined length of time and that, during such activation, it will adhesively hold the insole to the bottom and upon tie-activation it will become nonadhesive and release the insole. Preferably the material is further characterized in that it has an appreciable coefiicient of expansion so that it is expanded during activation into intimate contact with the insole when the latter is placed against the bottom of the last and when de-activated contracts, pulling away from the insole so as to detach itself therefrom, leaving no residue on the surface of the insole. Thermoplastic materials are effective for this purpose and may be activated for pre-, determined lengths of time by suitable means. The material may be attached mechanically or by a permanent adhesive.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 shows the bottom of the last;

FIG. 2 is an elevation partly in section;

FIG. 3 is a fragmentary section of the last, showing the thermoplastic lasting adhesive expanded; and

FIG. 4 is a corresponding section showing the thermoplastic adhesive de-activated and retracted, releasing the last for removal from the lasted shoe.

Referring to the drawings, the last is provided at its bottom with a plurality of holes 12, for example similar to those conventionally employed for receiving plugs or inserts of metal, cork, plastic or the like, into which tacks may be driven to hold the insole on the bottom. In accordance with this invention however a material 14 is disposed in each hole 12, so that the upper surface 16 of the material is slightly below the bottom surface of the last (FIG. 2). In order to anchor the material in the hole 12 the wall of the latter is provided with indentations 18 which may be circular or thread-like. Optionally, the material 14 can be anchored in a smooth hole by means of a permanent adhesive, for example a thermosetting material.

ited States atent 3,089,166 Patented May 14, 1963 The material used is thermoplastic as distinguished from thermosetting, is normally solid, and is characterized in that it can be repeatedly activated so as to become adhesive and de-activated to become non-adhesive, that the period between activation and de-activation may be predetermined and that the material expands appreciably upon activation and contracts upon de-a-ctivation. The organic thermoplastics which have a high linear coefiicient of thermal expansion are preferred for this purpose, such as nylon, ethylene, vinylidene chloride, and the like. An example of a suitable thermoplastic is a commercial polyamide resin manufactured and supplied by General Mills, Inc., under'the name of Versalon XRSOl. Activation of the thermoplastic is preferably affected by induction heatmg.

In use, an insole 20 is placed upon the bottom surface of the last whereupon the last, with the insole thereon, is inserted into a heater. When the material 14 in the several holes is sufliciently activated to expand the operator removes the last from the heater and presses the insole 20 against the now adhesive material which holds it in contact with the last. The activated condition of the thermoplastic exists for a predetermined length of time which may be adjusted by using a suitable composition so that the insole is held in position for a length of time sufiicient to accomplish that lasting operation. Ultimately, the material will become de-activated and, by contraction and loss of its adhesivenes, pull itself away from the insole, leaving the latter free as disclosed, for example, in FIG. 4.

The inserts of thermoplastic are shown in FIG. 1 as disposed lengthwise of the bottom along the median line, however, this is not to be considered as limiting as it is within the scope of the invention to place them laterally of the median line and to employ a greater or lesser number of inserts than are shown.

In a less desirable but still operable form of the invention, a thin layer of the thermoplastic material is applied to the entire bottom of the last or only a part thereof. The layer is secured to the bottom of the last by a thermosetting material which adheres permanently and is not eifected by the activation of the thermoplastic layer. As described above, the thermosplastic may be repeatedly made adhesive by activation and, after a cooling period, become de-activated and non-adhesive and, by its contraction, relative to its surface contact with the insole, detaches itself from the surface of the insole leaving the latter free.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. The combination with a last for receiving an upper assembly including an insole preparatory to lasting, of means for releasably holding the insole on the bottom during the lasting operation, comprising a material secured to the bottom. of the last, said material being characterized in that it is repeatedly activatable without diminution, that during each activation it will adhesively hold the insole to the bottom, and that upon de-activation it will become non-adhesive and will release the insole.

2. The combination with a last for receiving an upper assembly including an insole preparatory to lasting, of means for releasably holding the insole on the bottom during the lasting operation, comprising a material attached to the bottom of the last, characterized in that it is activatable by heat for a predetermined length of time and will become de-act-ivated at the end of said time and, during activation, it will adhesively hold the insole to tlhe bottom and upon de-activation will release the mso e.

3. The combination with a last for receiving an upper assembly including an isole preparatory to lasting, of means for releasably holding the insole on the bottom during the lasting operation, comprising a material attached to the bottom of the last, characterized in that it is 'activatable by high frequency current for a predetermined time and it will then become de-activated, that during such activation it will adhesively hold the insole to the bottom and upon de-activation will release the insole. 4. The combination with a last for receiving an upper assembly including an insole preparatory to lasting, of substantially permanently reuseable means for releasably holding the insole on the bottom during the lasting operation, comprising a material attached to the bottom, characterized in that it is repeatedly activatable without diminution, that it expands during activation and becomes adhesive, and that it contracts during de-activation and becomes non-adhesive.

5. The combination with a last for receiving an upper assembly including an insole preparatory to lasting having a plurality of holes in its bottom, of an activatable material filling each hole, the upper surface of which is situated slightly below the level of the bottom of the last, characterized in that, when activated, it expands so as to project from the hole into adhesive contact with the insole i and upon deactivation it contracts into the hole releasing the insole.

6. A last according to claim 5, wherein the inner surface of the hole is provided with depressions for anchoring the material therein.

7. A last according to claim 5, wherein the material in the holes has a relatively high linear coefiicient of expansion.

8. The combination with a last for receiving an upper assembly including an insole preparatory to lasting, of a substantially permanently reuseable layer of thermoplastic material applied to at least a portion of the whole of the bottom surface by means of a thermosetting adhesive, said thermoplastic layer being characterized in that it is repeatedly activatable without diminution, that during activation it expands and becomes adhesive and that when d'e-activated it becomes non-adhesive and contracts.

References Cited in the file of this patent UNITED STATES PATENTS 1,365,221 Blake Jan. 11, 1921 2,893,026 Sillars et al July 7, 1949 FOREIGN PATENTS 782,690 Great Britain Sept. 11, 1957 

1. THE COMBINATION WITH A LAST FOR RECEIVING AN UPPER ASSEMBLY INCLUDING AN INSOLE PREPARATORY TO LASTING, OF MEANS FOR RELEASABLY HOLDING THE INSOLE ON THE BOTTOM DURING THE LASTING OPERATION, COMPRISING A MATERAL SECURED TO THE BOTTOM OF THE LAST, SAID MATERIAL BEING CHARACTERIZED IN THAT IT IS REPEATEDLY ACTIVATABLE WITHOUT DIMINUTION, THAT DURING EACH ACTIVATION IT WILL ADHESIVELY HOLD THE INSOLE TO THE BOTTOM, AND THAT UPON DE-ACTIVATION IT WILL BECOME NON-ADHESIVE AND WILL RELEASE THE INSOLE. 